The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Aspects of the invention relate to an apparatus for performing operations, in particular cutting, embossing, creasing, folding and/or sealing, on a moving web, typically of paper, cardboard or laminated material and provided with images, typically a series of identical images, which apparatus comprises a sensor for at least partially detecting the images on the web, and a processing unit which, dependent on a comparison of data obtained with the sensor and a reference, generates an output signal to be used for one or more of the said operations. The invention further relates to a module for use in the said apparatus, to a method of generating an output signal to be used for one or more apparatus operations, and to a roll of web material.
As explained in international patent application WO 97/29453, it is already known in the art to control processing operations on a moving material strip by means of control marks printed-on the strip, which marks can be detected by photocells or other optical devices. The marks are usually printed in a color tone which contrasts with the surroundings, thus enabling the detection means to detect the exact position of e.g. printed patterns and defining the current position of the material strip. This information can serve e.g. to ensure that subsequently applied crease line patterns coincide with the printed patterns and that the folding of the material takes place along these crease lines.
U.S. Pat. No. 4,600,841 relates to a mark detector for detecting marks on a running web distinguished from any printed letter or pattern or any printing smudge. The width of mark segments and the distance between them are determined and, if they are within preset ranges, a mark detection signal is given. A delayed signal generator and a false signal generator are provided.
DE 33 32 750 relates to a color mark probe, which is constructed in such a way that both the balancing on the background of the material to be scanned and the bright/dark switchover can be performed fully electronically from outside without operating actions.
The presence of control marks in the end product, be it a carton holding a liquid or sachets containing a powder, is generally undesirable. Hence, control marks are usually kept relatively small and are located e.g. on the bottom of a carton or on the seals of a sachet.